Communication systems typically comprise a plurality of dispatch consoles and communication units, such as mobile or portable radio units, that are geographically distributed among various base sites and console sites. The communication units wirelessly communicate with the dispatch consoles and each other via repeaters. The repeaters receive transmissions from the communication unit and wirelessly retransmit them to the other communication units or retransmit them by wire to the dispatch consoles. The communication units and dispatch consoles are often logically divided into various talkgroups. Communication systems may be organized as trunked systems, where a plurality of radio frequency (RF) communication resources are allocated amongst multiple users or groups by assigning the base sites and RF channels within a coverage area on a call-by-call basis, or as conventional (non-trunked) systems where RF communication resources are dedicated to one or more users or groups. In trunked systems, or in mixed trunked and conventional systems, there is usually provided a controller/server (sometimes called a “zone controller”) for allocating RF communication resources among a group of sites. The zone controller may reside within a single device, or multiple devices, and may be located at a fixed equipment site or may be distributed among the base sites.
Calls among the communication units are typically of the dispatch type, or better known as push-to-talk (PTT). Each time a communication unit is keyed to begin a call, the call is assigned to an available wireless RF channel. The originating communication unit begins transmitting on the assigned RF channel and continues to transmit on the assigned RF channel until the communication unit has been dekeyed by the user. Other communication units in an associated talkgroup also begin listening to the call. Each RF channel may have a pair of frequencies associated with it, an outgoing frequency and an incoming frequency. All communications transmitted by the communication units are made on the incoming frequency. All communications originating from a dispatch console or being wirelessly retransmitted by the repeater are made on the outgoing frequency. In other examples, incoming and outgoing channels may be accessed by time (TDMA) or code (CDMA).
In current communication systems, there is often a need to support multiple talkgroups on a single RF channel. As a result, it becomes a challenge to manage multiple users all on a single RF channel, including some users in the same or different talkgroups, since it often requires interrupting one communication with another communication or waiting for one to finish before starting another. When the communication units are at different sites, the network may be reconfigured to allow audio from an interrupting communication unit to be the source of the call. If the interrupting communication unit is at the same base site as the communication unit being interrupted, one of three outcomes may occur based on the RF characteristics of the system: 1) the transmission from the interrupted communication unit is heard as opposed to the interrupting communication unit, 2) the transmission from the interrupting communication unit is heard as opposed to the interrupted communication unit or 3) the transmissions from the two communication units interfere with each other, and no audio is heard. As a result, some current communication systems have been modified so as to allow only one communication unit at a time to transmit a communication while requiring other communication units to provide users with an indication that a communication is being transmitted and that they cannot currently transmit a communication.
Accordingly, many current communications do not have an effective way of dealing with overlapping communications of different talkgroups on the same multi-talkgroup channel. Current communication systems do not adequately make provisions for interactions between dispatch-console-initiated transmissions and subscriber-initiated transmissions on different talkgroups all using the same multi-talkgroup channel. Some current communication systems, as discussed above, may prevent all transmissions on a channel, without regard to user group separation, when any communication unit or dispatch console is transmitting a communication. However, there is little flexibility in the communication system for effectively managing overlapping communications from multiple talkgroups on the same multi-talkgroup channel.
For example, in the case of a single multi-talkgroup channel partitioned into a Talkgroup A and a Talkgroup B, it is possible that a dispatcher could initiate a voice transmission or communication on Talkgroup A, without realizing that there is already traffic on the multi-talkgroup channel from Talkgroup B. As used herein, the term “traffic” refers to any ongoing communications being transmitted on a channel, such as by the dispatcher on a dispatch console or a user on a communication device. The interaction of different communications on different talkgroups (Talkgroups A and B) on a conventional channel could result in behavior that is unanticipated by the dispatcher. This behavior could occur unknowingly to the dispatcher if his/her particular dispatch console is not subscribed to transmit and/or receive traffic in, or subscribed to participate in, the talkgroup that is currently using the channel. For example, the dispatcher, while on Talkgroup A, would not necessarily be able to hear any audio or communication on Talkgroup B which would conflict with her transmission on Talkgroup A. This scenario is likely to occur in a communication system that shares a single multi-talkgroup channel amongst users in multiple agencies. In that case, the dispatch console would likely be subscribed to participate in only the talkgroup or talkgroups on the multi-talkgroup channel pertinent to that dispatch console's users or agency, and not talkgroups being used by a sharing agency or other users.
Accordingly, there is a need for an improved method and apparatus for informing a dispatcher of conventional traffic in different talkgroups all using a single multi-talkgroup channel.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.